Funny. I guess I already fixed this without knowing it. I redid some of the resolution stuff to allow for window resizing.
Edit: Or not. For some reason, the first time I tried, the screenshot took OK, but it was messed up after that.
Apparently 1366x768 is a weird resolution that causes the data alignment to be off. I've put in something that appears to fix it. In the mean time, use a different resolution, if you can.